First-trimester screening for Down syndrome with ductus venosus Doppler studies in addition to nuchal translucency and serum markers

OBJECTIVE: To estimate the improvement in screening efficiency when fetal ductus venosus Doppler studies are added to existing first-trimester Down syndrome screening protocols. METHODS: Statistical modelling was used with parameters derived from prospective ductus venosus studies and from the published literature. The pulsatility index for veins (PIV), was determined in the fetal ductus venosus for 3706 unaffected and 25 Down syndrome pregnancies at 10-14 weeks' gestation. Concurrent nuchal translucency measurement and maternal serum pregnancy associated plasma protein A and free-beta human chorionic gonadotrophin were also measured. RESULTS: The median PIV in Down syndrome was 1.70 times higher than in unaffected pregnancies (95% confidence interval 1.36-2.12). PIV levels followed an approximately log Gaussian distribution with log(10) standard deviations of 0.193 and 0.076 in Down syndrome and unaffected pregnancies. There were no statistically significant correlations between PIV and the other markers. Modelling predicts that for a fixed 5% false-positive rate, the addition of PIV to nuchal translucency alone will increase the detection rate from 76 to 85%, and combined with serum markers, from 88 to 92%. For a fixed 85% detection rate, the false-positive rate reduced from 15 to 4.8% and from 3.2 to 1.2% respectively. CONCLUSION: Ductus venosus Doppler studies can substantially improve Down syndrome screening efficiency.     

First-trimester fetal nuchal translucency and inherited metabolic disorders

OBJECTIVES: To assess the association between inherited metabolic disorders and nuchal translucency (NT) measurements. METHODS: The NT measurements obtained from 66 fetuses at high risk for metabolic diseases prior to chorionic villus sampling (CVS) were retrospectively analysed. RESULTS: NT was found to be within the normal range in all of the 13 affected fetuses, which included three with Gaucher disease, two with glycogenosis type II, two with mucopolysaccharidosis type I and six others with Krabbe disease, metachromatic leukodystrophy, mucopolysaccharidosis type II, Niemann-Pick A disease, Pelizaeus-Merzbacher disease and sialidosis, respectively. An increased nuchal thickness was found only in one fetus affected with trisomy 21 but not affected with mucopolysaccharidosis type II. CONCLUSION: NT appears to have a limited role in identifying affected fetuses in pregnancies at high risk for inherited metabolic disorders. NT may be normal in early pregnancy even for fetuses affected with conditions known to be associated with non-immune hydrops fetalis.     

First-trimester Down's syndrome screening by fetal nuchal translucency measurement in Taiwan.

BACKGROUND: Fetal nuchal translucency (NT) measurement is now widely used in many Western countries as a screening tool for Down's syndrome during the first trimester. However, at present there is no data on its use in Taiwan. The purpose of the present study was to evaluate the efficacy of NT measurement in first-trimester Down's syndrome screening in Taiwan. METHODS: We conducted a prospective study from October 1997 to May 1999. Sonographic measurement of fetal NT was performed in 1,249 fetuses at 9-14 weeks of gestation. Transabdominal ultrasound scanning was performed to obtain a sagittal section of the fetus for measuring the crown-rump length (CRL) and the maximum thickness of the subcutaneous translucency between the skin and the soft tissue overlying the cervical spine. Two different cut-off points were used for screening: a fixed cut-off point of at least 2.5 mm and a CRL-related cut-off point. In the latter method, fetuses with an NT measurement in the 95th percentile were considered at high risk for Down's syndrome. RESULTS: Three fetuses had Down's syndrome, with NT measurements of 2.1 mm, 2.7 mm, and 4.0 mm. The false positive rates for the fixed cut-off point and CRL-related cut-off point were 6.3% and 4.6%, respectively. Both methods had a sensitivity of 66.7%. However, the screening program using the CRL-related cut-off point had two advantages: a higher specificity (95.5% vs 93.8%) and a more reasonable distribution pattern for screening. CONCLUSION: This study showed that NT measurement is a potential screening tool for Down's syndrome during the first trimester in Taiwan. Using CRL-related cut-off points for screening is more reasonable than using a fixed cut-off point.     

Changes in nuchal translucency thickness in normal and abnormal karyotype fetuses

Objective To investigate the dynamic trend of the nuchal translucency thickness between fetuses with normal and abnormal karyotype.
Design Prospective observational study.
Setting Ospedale Microcitemico, Cagliari, Italy.
Population A cohort of 305 first trimester fetuses.
Methods Fetuses with a nuchal translucency greater than or equal to the 95th centile were invited for a second nuchal translucency measurement. The finding of an 'increased or unchanged' or 'diminished' thickness was compared in fetuses with normal and abnormal karyotype.
Main outcome measures Nuchal translucency and karyotype.
Results Median maternal age was 35 years (min 17, max 44) and median crown–rump length at first visit was 50 mm (min 38, max 80). A second nuchal translucency measurement was carried out in 292 fetuses, resulting in increased or unchanged values in 95 cases and decreased nuchal translucency in 197 cases. Two hundred and twenty-six (77.4%) fetuses had normal karyotype and 66 (22.6%) had abnormal karyotype (44 trisomies 21, 10 trisomies 18, 5 trisomies 13, 4 cases of 45 X0, 1 case of 47,XXY, 1 case of 47,XXX and 1 translocation). In the 66 chromosomally abnormal fetuses, the second nuchal translucency measurement was enlarged or unchanged in 37 (56%), and diminished in 29 (44%), while in the 226 normal fetuses the second nuchal translucency measurement was enlarged or unchanged in 58 cases (25%) and diminished in 168 (75%) (relative risk 2.6, 95% confidence interval 1.7–4.0).
Conclusion In fetuses with abnormal karyotype, the second nuchal translucency measurement tends to be increased or unchanged, while in normal cases the size of nuchal translucency is generally reduced.     

First-trimester ultrasonographic screening for trisomy 21 using fetal nuchal translucency and nasal bone

OBJECTIVE: To report our experience with first-trimester screening for trisomy 21 by using the combination of nuchal translucency thickness and nasal bone assessment. METHODS: Pregnant women from a predominantly Latin American population consisting of patients at both low risk and high risk for chromosomal defects underwent first-trimester ultrasonographic screening. Nuchal translucency thickness and nasal bone were assessed by two accredited fetal medicine specialists. Cases of trisomy 21 were identified from the cytogenetics laboratory logbook. RESULTS: Over a 3-year period, 1,287 consecutive singleton pregnancies were screened. The median maternal age was 33 years (range 14-47 years), with 456 (35.4%) women aged 35 years or older at the time of the scan. Overall, 110 fetuses (8.5%) had nuchal translucency thickness greater than the 95th percentile for gestational age and 25 (1.9%) had absent nasal bone. Trisomy 21 was diagnosed in 31 cases. Among them, the nuchal translucency thickness was increased in 28 and the nasal bone was absent in 13 (detection rates of 90.3% and 41.9%, respectively; P<.01). All but one (92.3%) of the trisomy 21 fetuses with absent nasal bone had increased nuchal translucency. Only two of the normal fetuses had an absent nasal bone in the first trimester. CONCLUSION: In our population, increased nuchal translucency thickness is the most important ultrasonographic marker of trisomy 21. In contrast, the nasal bone seems to have a less prominent role in identifying the fetus at risk for trisomy 21 due to its lower detection rate. However, an absent nasal bone should be considered as a highly predictive marker of trisomy 21.     

First-trimester fetal heart block and increased nuchal translucency: an indication for early fetal echocardiography

Prevalence of congenital heart disease increases with nuchal translucency (NT) thickness. First-trimester fetal bradycardia may result from heart block associated with complex congenital heart disease. We report two cases detected in the first trimester of pregnancy, in which both fetuses showed an increased nuchal translucency and bradycardia. Fetal karyotype was normal in both fetuses. First-trimester fetal echocardiography was performed and, in both cases, complex congenital heart disease was diagnosed. We discuss the added role of fetal heart rate in first-trimester ultrasound screening, in fetuses with increased nuchal translucency and normal karyotype. We stress, as well, the importance of echocardiography performed in the first trimester as a potential tool for early diagnosis in selected cases.     

Relation between increased fetal nuchal translucency thickness and chromosomal defects

OBJECTIVE: To examine the prevalence and distribution of all chromosomal defects in fetuses with increased nuchal translucency thickness. METHODS: Assessment of risk for trisomy 21 was carried out by a combination of maternal age and fetal nuchal translucency thickness at 11-13 + 6 weeks. A search of the database was made to identify, first, all singleton pregnancies in which fetal karyotyping was carried out and, second, the cases where the fetal nuchal translucency was equal to or above the 95th centile for fetal crown-rump length. The prevalence and distribution of chromosomal defects were determined for each nuchal translucency category: between the 95th centile for crown-rump length and 3.4 mm, 3.5-4.4 mm, 4.5-5.4 mm, 5.5-6.4 mm, 6.5-7.4 mm, 7.5-8.4 mm, 8.5-9.4 mm, 9.5-10.4 mm, 10.5-11.4 mm, and 11.5 mm or more. RESULTS: The search identified 11,315 pregnancies. The median maternal age was 34.5 (range 15-50) years, and the median fetal crown-rump length was 64 (range 45-84) mm. The fetal karyotype was abnormal in 2,168 (19.2%) pregnancies, and the incidence of chromosomal defects increased with nuchal translucency thickness from approximately 7% for those with nuchal translucency between the 95th centile for crown-rump length and 3.4 mm to 75% for nuchal translucency of 8.5 mm or more. In the majority of fetuses with trisomy 21, the nuchal translucency thickness was less then 4.5 mm, whereas in the majority of fetuses with trisomies 13 or 18 it was 4.5-8.4 mm, and in those with Turner syndrome it was 8.5 mm or more. CONCLUSION: In fetuses with increased nuchal translucency, approximately one half of the chromosomally abnormal group is affected by defects other than trisomy 21. The distribution of nuchal translucency is different for each type of chromosomal defect. LEVEL OF EVIDENCE: II-3.     

First-trimester screening for Down syndrome in France combining fetal nuchal translucency measurement and biochemical markers

BACKGROUND: In France, there is a strictly regulated National Screening Programme for Down syndrome, based on second-trimester maternal serum markers. A prospective study of nuchal translucency together with retrospective evaluation of maternal serum markers was carried out to inform decisions on whether to move the programme to the first trimester. METHODS: Between January 1998 and June 2001, all women who presented for their prenatal care at 12 participating maternity units were, regardless of age, invited to provide a blood sample and to attend for an NT scan at 11 to 13 weeks. The results were used to derive Gaussian distribution parameters. Detection and false-positive rates were computed in two ways: statistical modelling and directly. The cut-off risk was 1 in 250 at term. RESULTS: A total of 5694 women with singleton pregnancies were screened including 26 with Down syndrome and 24 with other aneuploidies. The model-predicted detection and false-positive rates for combined ultrasound and serum screening were 81 and 4.5% compared to 64 and 6.0% for ultrasound alone. The directly observed rates were 73 and 4.7%, compared to 62 and 5.0% respectively. CONCLUSION: In France, first-trimester screening with nuchal translucency and maternal serum markers is likely to achieve a high screening efficiency. This has important implications for the national screening policy.     

Ductus venosus flow velocities in relation to the cardiac defects in first-trimester fetuses with enlarged nuchal translucency

OBJECTIVE: Our aim is to study first-trimester ductus venosus (DV) velocities in relation to cardiac abnormalities. STUDY DESIGN: Ultrasound examination was performed in 85 normal fetuses and 45 fetuses with a nuchal translucency (NT) >95th percentile. Pulsatility index for veins (PIV) and velocity during late diastole (a-V) of the DV were measured and compared with the use of multilevel analysis, between fetuses with a heart defect and those without. RESULTS: Compared with 85 normal fetuses, the a-V and PIV of the fetuses with NT>95th percentile and normal hearts were decreased and increased, respectively. The a-V and PIV of 11 fetuses with NT>95th percentile and cardiac defects were decreased and increased compared with the 25 fetuses with normal hearts, irrespective of the karyotype. The most common cardiac malformations were septal defects. CONCLUSION: Fetuses with NT >95th percentile and cardiac defects show markedly changed DV velocities. Because the type of cardiac defects cannot always explain the hemodynamic changes found in these fetuses, some other mechanisms seem to be involved.     

Ductus venosus assessment at the time of nuchal translucency measurement in the detection of fetal aneuploidy

OBJECTIVE: To assess the potential value of ductus venosus Doppler studies in the detection of fetal aneuploidy on measurement of nuchal translucency. METHODS: The pulsatility index for veins (PIV) and the lowest velocity during atrial contraction (A-wave) were determined in the fetal ductus venosus in 3382 consecutive pregnancies at 10 to 14 weeks and studied from December 1996 to December 2001. Nuchal translucency was also measured. The population studied included 1664 pregnancies at high risk and 1718 at low risk for fetal aneuploidy. RESULTS: In relation to the prenatal detection of trisomy 21, the ductus venosus PIV was increased in 75% (36/48), the A-wave was decreased in 58% (28/48), and nuchal translucency was enlarged in 81% (39/48) of the trisomy 21 fetuses [71% (22/31) when nuchal translucency referrals were excluded]. The corresponding figures for trisomies 18 and 13 were 71, 58 and 83%, respectively, being 33, 33 and 33% for other unbalanced anomalies. CONCLUSION: There is a high proportion of fetuses with trisomies 21, 18 and 13 (around 75%) in which the ductus venosus PIV is increased (above the 95th percentile) at 10 to 14 weeks, this proportion being similar to that observed for increased nuchal translucency measurement.     

Screening performance of first trimester nuchal translucency, ductus venosus blood flow and tricuspid regurgitation for cardiac defects

The present article summarises current knowledge on the risk of fetal cardiac malformations in fetuses with increased nuchal translucency (NT), abnormal ductus venosus blood flow pattern and tricuspid regurgitation. The risk of congenital heart disease (CHD) increases with increasing NT. However, nuchal translucency screening is only modestly efficient in the detection of congenital heart disease in low-risk pregnancies. If the nuchal translucency is normal, abnormal ductus venosus blood flow and tricuspid regurgitation show low sensitivities as single screening parameters. The combination of all 3 markers might increase the detection rates. Fetal echocardiography at 20 weeks of gestation is recommended in foetuses with an NT ≥95th percentile, as the incidence of CHD increases 2.5-fold. When the NT measurement is ≥99th percentile, the risk of CHD increases 10-fold. In this high-risk group and in fetuses with tricuspid regurgitation and/or an abnormal DV flow pattern along with an increased NT, first or early second trimester echocardiography performed by experts is warranted. The early examination of the fetal heart should be completed by a detailed echocardiogram at around 20 weeks of gestation.     

First-trimester Down syndrome screening using dried blood biochemistry and nuchal translucency

OBJECTIVE: To assess the effectiveness of free beta-hCG, pregnancy-associated plasma protein A, and nuchal translucency in a prospective first-trimester prenatal screening study for Down syndrome and trisomy 18. METHODS: Risks were calculated for Down syndrome and trisomy 18 based on maternal age and biochemistry only (n = 10,251), nuchal translucency only (n = 5809), and the combination of nuchal translucency and biochemistry (n = 5809). RESULTS: The study population included 50 Down syndrome and 20 trisomy 18 cases. Nuchal translucency measurement was done on 33 Down syndrome and 13 trisomy 18 cases. Down syndrome screening using combined biochemistry and ultrasound resulted in a false-positive rate of 4.5% (95% confidence interval [CI] 3.9%, 5.2%) and detection rate of 87.5% (95% CI 47%, 100%) in patients under age 35 years. In older patients, the false-positive rate was 14.3% (95% CI 12.7%, 15. 8%) and detection rate was 92% (95% CI 74%, 99%). For trisomy 18 screening, the false-positive rate was 0.4% (95% CI 0.24%, 0.69%) and detection rate was 100% (95% CI 40%, 100%) in younger patients, whereas in older patients the false-positive rate was 1.4% (95% CI 0. 9%, 2.0%) and detection rate was 100% (95% CI 66%, 100%). Using modeling, at a fixed 5% false-positive rate, the Down syndrome detection rate was 91%. Conversely, at a fixed 70% Down syndrome detection rate, the false-positive rate was 1.4%. CONCLUSION: First-trimester screening for Down syndrome and trisomy 18 is effective and offers substantial benefits to clinicians and patients.     

Association between fetal nuchal translucency thickness in first trimester and subsequent gestational hypertension and preeclampsia

Increased fetal nuchal translucency (NT) in the first trimester is associated with adverse pregnancy outcomes. Whether the increased NT is also associated with an increased frequency of pregnancy-associated hypertension (PAH) is not known. Seven hundred and seventy-nine pregnant women who received NT-based Down syndrome screening and delivered their babies at our hospital by September 2000 were enrolled into this study. Among these women, there are 46 cases of preeclampsia, 68 cases of gestational hypertension (GH); 665 women without any adverse pregnancy outcomes served as controls. Correlation analysis demonstrated that NT MoM (multiples of median) level had a positive association with maternal diastolic blood pressure at the time of admission for delivery (r = 0.104; p < 0.01). The severity of PAH was concordant with the stepwise increase of mean NT MoM level, which was 0.88 in control, 1.07 in gestational hypertension, and 1.13 in preeclampsia (p < 0.001). Using the 95th (1.52 MoM) and 90th (1.31 MoM) percentiles of NT thickness as cut-offs, the sensitivities and odds ratios of the women at risk for developing GH after 20 weeks of gestation were 8.8%, 19.1% and 1.98, 2.15 respectively, while for preeclampsia were 10.9%, 28.3% and 2.49, 3.58 respectively. It is concluded that the pathological changes in the placenta responsible for the development of PAH may also influence the physiological decrease of NT thickness in late first trimester. However, the sensitivity of fetal NT measurement in first trimester is not sufficient as a single marker for predicting the pregnant women at risk for subsequent PAH.